Аннотация:Strontium is isomorphic to calcium, so it is easy accumulated in a human bone tissue. Background content of soluble strontium in natural waters does not exceed 7-8 mg/l. This level of strontium content is acceptable for humans. However, pollutions of water with radioactive strontium (90Sr) as a result of accidents at a nuclear power station or burial of radioactive waste lead to a dramatic increase in Sr concentration in natural waters. Fast and sensitive methods for determination of strontium in natural waters without any sample preparation are necessary for rapid monitoring and mapping of the contamination level of sea or ocean waters. Since strontium is easy to excite, its determination by means of emission methods has high sensitivity. Laser-Induced Breakdown Spectrometry is proposed in this work for fast and direct determination of strontium in sea waters.
To simulate sea water, a model solution was prepared with high purity reagents (NaCl - 26.6 g/l, CaCl2 - 1.8 g/l, KCl - 0.8 g/l, MgSO4 - 5.7 g/l). Strontium was added to this solution in a form of dry powder of SrCl2×6H2O to produce a number of solutions with strontium content varying from 0 to 450 mg/l (i.e. 450 ppm). Three analytical lines of strontium (Sr II 407.77 nm, Sr II 421.55 nm and Sr I 460.73 nm) were examined for the determination of this element. Comparison of analytical results of the measurements for the two harmonics of Nd:YAG laser (355 nm and 532 nm) showed that there were not differences in sensitivity and stability between these harmonics after a choice of proper experimental conditions. The limit of detection of strontium in sea water was 200 μg/l (i.e. 200 ppb) for the line of Sr II at 407.77 nm. RSD of Sr line in model solutions at low strontium content (2 mg/l) did not exceed 15 %. There were significant matrix effects for the analysis of aqueous solutions of strontium and solutions simulating sea water. The limit of detection of strontium in pure aqueous solutions was 25 μg/l (i.e. 25 ppb). The developed technique was examined for analysis of seawater samples from different parts of the Arctic Ocean. The content of strontium in these waters varies in the range of 1.5-6 mg/l, which proves the possibility of direct quantification of strontium in seawater at background level by LIBS.